How should the regulation allowing substitution of batches for individual units be understood?
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For pressure vessels other than those covered by Paragraph 2 of this article, if the manufacturer can provide test data from welding test plates made from the same grade of material, using the same welding process (with the key welding parameters and additional key parameters remaining within the acceptable range; the same applies hereafter), and following the same heat treatment specifications, for 30 consecutive units (in cases where the same product is manufactured using different grades of material, or different welding processes, or different heat treatment procedures, two units may be considered as one set), and if such data prove that the welding quality is stable, then with the approval of the technical supervisor of the manufacturer, it is permissible to prepare welding test plates on a batch basis. The specific provisions are as follows: How should the red text mentioned above be interpreted? It would be best to provide a simple explanation of this passage – under what circumstances, according to this rule, can batch processing be used in place of individual processing? This post was last edited by kelan on 2009-4-11 08:16]
This is how I understand it: the same product uses materials of different grades； If a device is made of 20R and 20R+0Cr13, it can be treated as two separate products
For the same product made from materials of different grades, or evaluated using different welding processes, or subjected to different heat treatment specifications, separate welding test plates shall be prepared.
“If the same product is made from materials of different grades, evaluated using different welding processes, or subjected to different heat treatment specifications, it can be treated as two separate products. If all three factors are present, can it then be considered multiple products?
For the same device, when different grade materials are used, or different welding procedures are employed, or different heat treatment specifications are applied, a product test plate is prepared separately for each case.
Does that mean that (for the same product made from different grades of material, or evaluated using different welding processes, or subjected to different heat treatment specifications, it can be treated as two separate products)? In that case, it’s no longer possible to treat them as part of a batch? Can batch production be used in place of individual testing by simply providing qualified test plates and welding procedure qualifications?
The premise for treating them as two separate products is the existence of two test plates; otherwise, they cannot be treated as such. It’s important to grasp this premise first, and only after that can we discuss the issue of multiple test plates, which falls under the scope of process evaluation. If a single test plate is welded using two different methods, such as SAW + SMAW, then it should be considered as one product only, and it cannot be regarded as two separate products resulting from the SAW and SMAW welding methods
For the same tank, such as a glass-lined jacketed vessel, since different welding evaluation criteria are applied to the inner cylinder and the jacket – the inner cylinder being subjected to a heat treatment process at a temperature higher than its upper transformation temperature – this tank can be treated as two separate units: the inner cylinder counts as one unit (undergoing heat treatment), and the jacket counts as another unit. A total of 30 units can be accumulated for each type before they can be considered as one batch. In other words, as long as the welding procedure qualifications used for the two test plates produced from the same tank are different, they can be treated as two separate products for which cumulative values can be calculated
The more I talk about it, the more confused I get. I think 30 units refers to 30 identical product samples, not the actual products, right?
A batch for testing purposes is not just about product samples; it also involves process evaluation. Within the scope covered by the same process evaluation, they can all be considered as one batch. If we are talking about samples, then different thicknesses mean that the samples will definitely be different. Under such circumstances, even 10 years of work might not be enough to produce 30 samples of the same product
What does that 30 units refer to? “What does it mean that \"products of the same type but made from different grades of material, or evaluated using different welding processes, or subjected to different heat treatment specifications, can be treated as two separate products\"? I just think this sentence is ambiguous and really confusing.
This sentence is a bit hard to understand at first, but if you think about it carefully, if there are two test plates on one container, then regardless of the welding method or the material used, as long as two test plates are required by regulations, it can be treated as two separate products (what matters here is the number of test plates; they don’t have to belong to the same product). If my equipment has only one test plate, then there’s no reason to treat it as two products
Think of it this way: when you are working on product welding test plates, there should be a registration ledger for these test plates, with each one being recorded in it. When it’s necessary to treat a batch as equivalent to a single test plate, all one needs to do is select from the ledger; 30 test plates within the same scope of process evaluation can then be treated as a batch. Here, we need to talk again about the test plates welded using the two different welding methods. For example, in the case of test plates welded using SAW and SMAW, two welding process evaluations will be required (if it is a combined evaluation, then only one evaluation is needed; however, the vast majority of companies do not carry out combined evaluations). When applying for approval to treat batches of such test plates as individual units, the thickness of these test plates must fall within the scope of both corresponding process evaluations. Only those that meet this requirement can have their batches approved as individual units
It should refer to the same piece of equipment, such as separators with the same part number. However, if, due to project requirements, there is any difference in the materials used for these two pieces of equipment, or in their welding process evaluations or heat treatment procedures, then this rule cannot be applied; in other words, they cannot use the same welding test plate.
I think in that case it can’t be called the same device; rather, it’s two different devices.
It doesn’t have to be the same device, right?